Preparations of Mg or Mg alloy granules in a friable salt matrix are taught, e.g., in U.S. Pat. No. 4,186,000; U.S. Pat. No. 4,182,498 and U.S. Pat. No. 4,279,641. In those patents there are taught methods in which molten mixtures of Mg (or Mg alloy) and salts are processed in a manner such that when the melts are cooled to the point of being frozen, the Mg is in dispersed form within the salt mixture. It is also disclosed there that the friable salt matrix is broken up in a manner such that the round granules of Mg are freed from entrapment in the salt matrix for removal from the salt, except that there remains on each granule a tightly-bound protective salt layer.
In U.S. Pat. No. 4,186,000 and U.S. Pat. No. 4,279,641 (incorporated herein by reference) there is disclosed the freezing of the molten mixture of Mg and salts by the technique of pouring the melt onto a revolving chilled roller on a flaking machine where the melt freezes as a thin sheet and is broken up into flakes by the action of the scraper blade. It has been found that in some melts, there is a tendency for some of the molten Mg particles to "stretch" into elongated particles due to the gravity flow (slippage) down the roller surface before the Mg becomes frozen. Then when the Mg freezes, the elongated (sometimes "stringy") shape is retained by the frozen Mg; this is not a welcome result when it is desired that the Mg granules be round, or at least nearly round in shape.
In order to provide a chilled surface on which the molten mixture could be cooled on a continuous feed basis, while avoiding the adverse effects of gravity encountered by the sliding of the melt down the non-horizontal surface of a chilled roll, the present novel rotary table flaker was designed. This novel rotary cooling table (also called a rotary table flaker) may also be used for chilling other melts on a horizontal, moving surface from which they are scrapped by a blade after being appropriately chilled.